Move ESP8266 yield() out of InterruptLock

fixed incorrect values on DHT11 below 0 degrees celcius

DHT.cpp

@@ -7,6 +7,7 @@ written by Adafruit Industries
 #include "DHT.h"
 
 #define MIN_INTERVAL 2000
+#define TIMEOUT -1
 
 DHT::DHT(uint8_t pin, uint8_t type, uint8_t count) {
   _pin = pin;
@@ -18,17 +19,20 @@ DHT::DHT(uint8_t pin, uint8_t type, uint8_t count) {
   _maxcycles = microsecondsToClockCycles(1000);  // 1 millisecond timeout for
                                                  // reading pulses from DHT sensor.
   // Note that count is now ignored as the DHT reading algorithm adjusts itself
-  // basd on the speed of the processor.
+  // based on the speed of the processor.
 }
 
-void DHT::begin(void) {
+// Optionally pass pull-up time (in microseconds) before DHT reading starts.
+// Default is 55 (see function declaration in DHT.h).
+void DHT::begin(uint8_t usec) {
   // set up the pins!
   pinMode(_pin, INPUT_PULLUP);
   // Using this value makes sure that millis() - lastreadtime will be
   // >= MIN_INTERVAL right away. Note that this assignment wraps around,
   // but so will the subtraction.
-  _lastreadtime = -MIN_INTERVAL;
-  DEBUG_PRINT("Max clock cycles: "); DEBUG_PRINTLN(_maxcycles, DEC);
+  _lastreadtime = millis() - MIN_INTERVAL;
+  DEBUG_PRINT("DHT max clock cycles: "); DEBUG_PRINTLN(_maxcycles, DEC);
+  pullTime = usec;
 }
 
 //boolean S == Scale.  True == Fahrenheit; False == Celcius
@@ -39,15 +43,27 @@ float DHT::readTemperature(bool S, bool force) {
     switch (_type) {
     case DHT11:
       f = data[2];
+      if (data[3] & 0x80) {
+        f = -1 - f ;
+      }
+      f += (data[3] & 0x0f) * 0.1;
+      if(S) {
+        f = convertCtoF(f);
+      }
+      break;
+    case DHT12:
+      f = data[2];
+      f += (data[3] & 0x0f) * 0.1;
+      if (data[2] & 0x80) {
+        f *= -1;
+      }
       if(S) {
         f = convertCtoF(f);
       }
       break;
     case DHT22:
     case DHT21:
-      f = data[2] & 0x7F;
-      f *= 256;
-      f += data[3];
+      f = ((word)(data[2] & 0x7F)) << 8 | data[3];
       f *= 0.1;
       if (data[2] & 0x80) {
         f *= -1;
@@ -71,16 +87,15 @@ float DHT::convertFtoC(float f) {
 
 float DHT::readHumidity(bool force) {
   float f = NAN;
-  if (read()) {
+  if (read(force)) {
     switch (_type) {
     case DHT11:
-      f = data[0];
+    case DHT12:
+      f = data[0] + data[1] * 0.1;
       break;
     case DHT22:
     case DHT21:
-      f = data[0];
-      f *= 256;
-      f += data[1];
+      f = ((word)data[0]) << 8 | data[1];
       f *= 0.1;
       break;
     }
@@ -89,7 +104,15 @@ float DHT::readHumidity(bool force) {
 }
 
 //boolean isFahrenheit: True == Fahrenheit; False == Celcius
-float DHT::computeHeatIndex(float temperature, float percentHumidity, bool isFahrenheit) {
+float DHT::computeHeatIndex(bool isFahrenheit) {
+  float hi = computeHeatIndex(readTemperature(isFahrenheit), readHumidity(),
+    isFahrenheit);
+  return isFahrenheit ? hi : convertFtoC(hi);
+}
+
+//boolean isFahrenheit: True == Fahrenheit; False == Celcius
+float DHT::computeHeatIndex(float temperature, float percentHumidity,
+  bool isFahrenheit) {
   // Using both Rothfusz and Steadman's equations
   // http://www.wpc.ncep.noaa.gov/html/heatindex_equation.shtml
   float hi;
@@ -120,11 +143,11 @@ float DHT::computeHeatIndex(float temperature, float percentHumidity, bool isFah
   return isFahrenheit ? hi : convertFtoC(hi);
 }
 
-boolean DHT::read(bool force) {
+bool DHT::read(bool force) {
   // Check if sensor was read less than two seconds ago and return early
   // to use last reading.
   uint32_t currenttime = millis();
-  if (!force && ((currenttime - _lastreadtime) < 2000)) {
+  if (!force && ((currenttime - _lastreadtime) < MIN_INTERVAL)) {
     return _lastresult; // return last correct measurement
   }
   _lastreadtime = currenttime;
@@ -132,42 +155,55 @@ boolean DHT::read(bool force) {
   // Reset 40 bits of received data to zero.
   data[0] = data[1] = data[2] = data[3] = data[4] = 0;
 
+#if defined(ESP8266)
+    yield(); // Handle WiFi / reset software watchdog
+#endif
+
   // Send start signal.  See DHT datasheet for full signal diagram:
   //   http://www.adafruit.com/datasheets/Digital%20humidity%20and%20temperature%20sensor%20AM2302.pdf
 
   // Go into high impedence state to let pull-up raise data line level and
   // start the reading process.
-  digitalWrite(_pin, HIGH);
-  delay(250);
+  pinMode(_pin, INPUT_PULLUP);
+  delay(1);
 
-  // First set data line low for 20 milliseconds.
+  // First set data line low for a period according to sensor type
   pinMode(_pin, OUTPUT);
   digitalWrite(_pin, LOW);
-  delay(20);
+  switch(_type) {
+    case DHT22:
+    case DHT21:
+      delayMicroseconds(1100); // data sheet says "at least 1ms"
+      break;
+    case DHT11:
+    default:
+      delay(20); //data sheet says at least 18ms, 20ms just to be safe
+      break;
+  }
 
   uint32_t cycles[80];
   {
-    // Turn off interrupts temporarily because the next sections are timing critical
-    // and we don't want any interruptions.
-    InterruptLock lock;
-
     // End the start signal by setting data line high for 40 microseconds.
-    digitalWrite(_pin, HIGH);
-    delayMicroseconds(40);
+    pinMode(_pin, INPUT_PULLUP);
+
+    // Delay a moment to let sensor pull data line low.
+    delayMicroseconds(pullTime);
 
     // Now start reading the data line to get the value from the DHT sensor.
-    pinMode(_pin, INPUT_PULLUP);
-    delayMicroseconds(10);  // Delay a bit to let sensor pull data line low.
+
+    // Turn off interrupts temporarily because the next sections
+    // are timing critical and we don't want any interruptions.
+    InterruptLock lock;
 
     // First expect a low signal for ~80 microseconds followed by a high signal
     // for ~80 microseconds again.
-    if (expectPulse(LOW) == 0) {
-      DEBUG_PRINTLN(F("Timeout waiting for start signal low pulse."));
+    if (expectPulse(LOW) == TIMEOUT) {
+      DEBUG_PRINTLN(F("DHT timeout waiting for start signal low pulse."));
       _lastresult = false;
       return _lastresult;
     }
-    if (expectPulse(HIGH) == 0) {
-      DEBUG_PRINTLN(F("Timeout waiting for start signal high pulse."));
+    if (expectPulse(HIGH) == TIMEOUT) {
+      DEBUG_PRINTLN(F("DHT timeout waiting for start signal high pulse."));
       _lastresult = false;
       return _lastresult;
     }
@@ -191,8 +227,8 @@ boolean DHT::read(bool force) {
   for (int i=0; i<40; ++i) {
     uint32_t lowCycles  = cycles[2*i];
     uint32_t highCycles = cycles[2*i+1];
-    if ((lowCycles == 0) || (highCycles == 0)) {
-      DEBUG_PRINTLN(F("Timeout waiting for pulse."));
+    if ((lowCycles == TIMEOUT) || (highCycles == TIMEOUT)) {
+      DEBUG_PRINTLN(F("DHT timeout waiting for pulse."));
       _lastresult = false;
       return _lastresult;
     }
@@ -207,7 +243,7 @@ boolean DHT::read(bool force) {
     // stored data.
   }
 
-  DEBUG_PRINTLN(F("Received:"));
+  DEBUG_PRINTLN(F("Received from DHT:"));
   DEBUG_PRINT(data[0], HEX); DEBUG_PRINT(F(", "));
   DEBUG_PRINT(data[1], HEX); DEBUG_PRINT(F(", "));
   DEBUG_PRINT(data[2], HEX); DEBUG_PRINT(F(", "));
@@ -221,7 +257,7 @@ boolean DHT::read(bool force) {
     return _lastresult;
   }
   else {
-    DEBUG_PRINTLN(F("Checksum failure!"));
+    DEBUG_PRINTLN(F("DHT checksum failure!"));
     _lastresult = false;
     return _lastresult;
   }
@@ -235,14 +271,18 @@ boolean DHT::read(bool force) {
 // in the very latest IDE versions):
 //   https://github.com/arduino/Arduino/blob/master/hardware/arduino/avr/cores/arduino/wiring_pulse.c
 uint32_t DHT::expectPulse(bool level) {
+#if (F_CPU > 16000000L)
   uint32_t count = 0;
+#else
+  uint16_t count = 0; // To work fast enough on slower AVR boards
+#endif
   // On AVR platforms use direct GPIO port access as it's much faster and better
   // for catching pulses that are 10's of microseconds in length:
   #ifdef __AVR
     uint8_t portState = level ? _bit : 0;
     while ((*portInputRegister(_port) & _bit) == portState) {
       if (count++ >= _maxcycles) {
-        return 0; // Exceeded timeout, fail.
+        return TIMEOUT; // Exceeded timeout, fail.
       }
     }
   // Otherwise fall back to using digitalRead (this seems to be necessary on ESP8266
@@ -250,7 +290,7 @@ uint32_t DHT::expectPulse(bool level) {
   #else
     while (digitalRead(_pin) == level) {
       if (count++ >= _maxcycles) {
-        return 0; // Exceeded timeout, fail.
+        return TIMEOUT; // Exceeded timeout, fail.
       }
     }
   #endif

DHT.h

@@ -30,6 +30,7 @@ written by Adafruit Industries
 
 // Define types of sensors.
 #define DHT11 11
+#define DHT12 12
 #define DHT22 22
 #define DHT21 21
 #define AM2301 21
@@ -38,13 +39,14 @@ written by Adafruit Industries
 class DHT {
   public:
    DHT(uint8_t pin, uint8_t type, uint8_t count=6);
-   void begin(void);
+   void begin(uint8_t usec=55);
    float readTemperature(bool S=false, bool force=false);
    float convertCtoF(float);
    float convertFtoC(float);
+   float computeHeatIndex(bool isFahrenheit=true);
    float computeHeatIndex(float temperature, float percentHumidity, bool isFahrenheit=true);
    float readHumidity(bool force=false);
-   boolean read(bool force=false);
+   bool read(bool force=false);
 
  private:
   uint8_t data[5];
@@ -56,6 +58,7 @@ class DHT {
   #endif
   uint32_t _lastreadtime, _maxcycles;
   bool _lastresult;
+  uint8_t pullTime; // Time (in usec) to pull up data line before reading
 
   uint32_t expectPulse(bool level);
 
@@ -64,12 +67,15 @@ class DHT {
 class InterruptLock {
   public:
    InterruptLock() {
+#if !defined(ARDUINO_ARCH_NRF52)  
     noInterrupts();
+#endif
    }
    ~InterruptLock() {
+#if !defined(ARDUINO_ARCH_NRF52)  
     interrupts();
+#endif
    }
-
 };
 
 #endif

DHT_U.cpp

@@ -37,6 +37,9 @@ void DHT_Unified::setName(sensor_t* sensor) {
     case DHT11:
       strncpy(sensor->name, "DHT11", sizeof(sensor->name) - 1);
       break;
+    case DHT12:
+      strncpy(sensor->name, "DHT12", sizeof(sensor->name) - 1);
+      break;
     case DHT21:
       strncpy(sensor->name, "DHT21", sizeof(sensor->name) - 1);
       break;
@@ -57,6 +60,9 @@ void DHT_Unified::setMinDelay(sensor_t* sensor) {
     case DHT11:
       sensor->min_delay = 1000000L;  // 1 second (in microseconds)
       break;
+    case DHT12:
+      sensor->min_delay = 2000000L;  // 2 second (in microseconds)
+      break;
     case DHT21:
       sensor->min_delay = 2000000L;  // 2 seconds (in microseconds)
       break;
@@ -105,6 +111,11 @@ void DHT_Unified::Temperature::getSensor(sensor_t* sensor) {
       sensor->min_value   = 0.0F;
       sensor->resolution  = 2.0F;
       break;
+    case DHT12:
+      sensor->max_value   = 60.0F;
+      sensor->min_value   = -20.0F;
+      sensor->resolution  = 0.5F;
+      break;
     case DHT21:
       sensor->max_value   = 80.0F;
       sensor->min_value   = -40.0F;
@@ -159,6 +170,11 @@ void DHT_Unified::Humidity::getSensor(sensor_t* sensor) {
       sensor->min_value   = 20.0F;
       sensor->resolution  = 5.0F;
       break;
+    case DHT12:
+      sensor->max_value   = 95.0F;
+      sensor->min_value   = 20.0F;
+      sensor->resolution  = 5.0F;
+      break;
     case DHT21:
       sensor->max_value   = 100.0F;
       sensor->min_value   = 0.0F;

README.md

@@ -1,15 +1,14 @@
-This is an Arduino library for the DHT series of low cost temperature/humidity sensors.
+# Adafruit DHT Humidity & Temperature Sensor Library
+
+An Arduino library for the DHT series of low cost temperature/humidity sensors.
 
 Tutorial: https://learn.adafruit.com/dht
 
-To download. click the DOWNLOADS button in the top right corner, rename the uncompressed folder DHT. Check that the DHT folder contains DHT.cpp and DHT.h. Place the DHT library folder your <arduinosketchfolder>/libraries/ folder. You may need to create the libraries subfolder if its your first library. Restart the IDE.
-
-# Adafruit DHT Humidity & Temperature Unified Sensor Library
-
-This library also includes an optional class for the
-[DHT humidity and temperature sensor](https://learn.adafruit.com/dht/overview)
-which is designed to work with the [Adafruit unified sensor library](https://learn.adafruit.com/using-the-adafruit-unified-sensor-driver/introduction).
-
-You must have the following Arduino libraries installed to use this class:
+**You must have the following Arduino libraries installed to use this class:**
 
 - [Adafruit Unified Sensor Library](https://github.com/adafruit/Adafruit_Sensor)
+
+Examples include both a "standalone" DHT example, and one that works along with the Adafruit Unified Sensor Library. Unified sensor library is required even if using the standalone version.
+
+Recent Arduino IDE releases include the Library Manager for easy installation. Otherwise, to download, click the DOWNLOADS button in the top right corner, rename the uncompressed folder DHT. Check that the DHT folder contains DHT.cpp and DHT.h. Place the DHT library folder your <arduinosketchfolder>/libraries/ folder. You may need to create the libraries subfolder if its your first library. Restart the IDE.
+

examples/DHT_Unified_Sensor/DHT_Unified_Sensor.ino

@@ -3,20 +3,22 @@
 // Written by Tony DiCola for Adafruit Industries
 // Released under an MIT license.
 
-// Depends on the following Arduino libraries:
-// - Adafruit Unified Sensor Library: https://github.com/adafruit/Adafruit_Sensor
+// REQUIRES the following Arduino libraries:
 // - DHT Sensor Library: https://github.com/adafruit/DHT-sensor-library
+// - Adafruit Unified Sensor Lib: https://github.com/adafruit/Adafruit_Sensor
 
 #include <Adafruit_Sensor.h>
 #include <DHT.h>
 #include <DHT_U.h>
 
-#define DHTPIN            2         // Pin which is connected to the DHT sensor.
+#define DHTPIN 2     // Digital pin connected to the DHT sensor 
+// Feather HUZZAH ESP8266 note: use pins 3, 4, 5, 12, 13 or 14 --
+// Pin 15 can work but DHT must be disconnected during program upload.
 
 // Uncomment the type of sensor in use:
-//#define DHTTYPE           DHT11     // DHT 11 
-#define DHTTYPE           DHT22     // DHT 22 (AM2302)
-//#define DHTTYPE           DHT21     // DHT 21 (AM2301)
+//#define DHTTYPE    DHT11     // DHT 11
+#define DHTTYPE    DHT22     // DHT 22 (AM2302)
+//#define DHTTYPE    DHT21     // DHT 21 (AM2301)
 
 // See guide for details on sensor wiring and usage:
 //   https://learn.adafruit.com/dht/overview
@@ -26,33 +28,32 @@ DHT_Unified dht(DHTPIN, DHTTYPE);
 uint32_t delayMS;
 
 void setup() {
-  Serial.begin(9600); 
+  Serial.begin(9600);
   // Initialize device.
   dht.begin();
-  Serial.println("DHTxx Unified Sensor Example");
+  Serial.println(F("DHTxx Unified Sensor Example"));
   // Print temperature sensor details.
   sensor_t sensor;
   dht.temperature().getSensor(&sensor);
-  Serial.println("------------------------------------");
-  Serial.println("Temperature");
-  Serial.print  ("Sensor:       "); Serial.println(sensor.name);
-  Serial.print  ("Driver Ver:   "); Serial.println(sensor.version);
-  Serial.print  ("Unique ID:    "); Serial.println(sensor.sensor_id);
-  Serial.print  ("Max Value:    "); Serial.print(sensor.max_value); Serial.println(" *C");
-  Serial.print  ("Min Value:    "); Serial.print(sensor.min_value); Serial.println(" *C");
-  Serial.print  ("Resolution:   "); Serial.print(sensor.resolution); Serial.println(" *C");  
-  Serial.println("------------------------------------");
+  Serial.println(F("------------------------------------"));
+  Serial.println(F("Temperature Sensor"));
+  Serial.print  (F("Sensor Type: ")); Serial.println(sensor.name);
+  Serial.print  (F("Driver Ver:  ")); Serial.println(sensor.version);
+  Serial.print  (F("Unique ID:   ")); Serial.println(sensor.sensor_id);
+  Serial.print  (F("Max Value:   ")); Serial.print(sensor.max_value); Serial.println(F("°C"));
+  Serial.print  (F("Min Value:   ")); Serial.print(sensor.min_value); Serial.println(F("°C"));
+  Serial.print  (F("Resolution:  ")); Serial.print(sensor.resolution); Serial.println(F("°C"));
+  Serial.println(F("------------------------------------"));
   // Print humidity sensor details.
   dht.humidity().getSensor(&sensor);
-  Serial.println("------------------------------------");
-  Serial.println("Humidity");
-  Serial.print  ("Sensor:       "); Serial.println(sensor.name);
-  Serial.print  ("Driver Ver:   "); Serial.println(sensor.version);
-  Serial.print  ("Unique ID:    "); Serial.println(sensor.sensor_id);
-  Serial.print  ("Max Value:    "); Serial.print(sensor.max_value); Serial.println("%");
-  Serial.print  ("Min Value:    "); Serial.print(sensor.min_value); Serial.println("%");
-  Serial.print  ("Resolution:   "); Serial.print(sensor.resolution); Serial.println("%");  
-  Serial.println("------------------------------------");
+  Serial.println(F("Humidity Sensor"));
+  Serial.print  (F("Sensor Type: ")); Serial.println(sensor.name);
+  Serial.print  (F("Driver Ver:  ")); Serial.println(sensor.version);
+  Serial.print  (F("Unique ID:   ")); Serial.println(sensor.sensor_id);
+  Serial.print  (F("Max Value:   ")); Serial.print(sensor.max_value); Serial.println(F("%"));
+  Serial.print  (F("Min Value:   ")); Serial.print(sensor.min_value); Serial.println(F("%"));
+  Serial.print  (F("Resolution:  ")); Serial.print(sensor.resolution); Serial.println(F("%"));
+  Serial.println(F("------------------------------------"));
   // Set delay between sensor readings based on sensor details.
   delayMS = sensor.min_delay / 1000;
 }
@@ -61,24 +62,24 @@ void loop() {
   // Delay between measurements.
   delay(delayMS);
   // Get temperature event and print its value.
-  sensors_event_t event;  
+  sensors_event_t event;
   dht.temperature().getEvent(&event);
   if (isnan(event.temperature)) {
-    Serial.println("Error reading temperature!");
+    Serial.println(F("Error reading temperature!"));
   }
   else {
-    Serial.print("Temperature: ");
+    Serial.print(F("Temperature: "));
     Serial.print(event.temperature);
-    Serial.println(" *C");
+    Serial.println(F("°C"));
   }
   // Get humidity event and print its value.
   dht.humidity().getEvent(&event);
   if (isnan(event.relative_humidity)) {
-    Serial.println("Error reading humidity!");
+    Serial.println(F("Error reading humidity!"));
   }
   else {
-    Serial.print("Humidity: ");
+    Serial.print(F("Humidity: "));
     Serial.print(event.relative_humidity);
-    Serial.println("%");
+    Serial.println(F("%"));
   }
 }

examples/DHTtester/DHTtester.ino

@@ -1,9 +1,15 @@
 // Example testing sketch for various DHT humidity/temperature sensors
 // Written by ladyada, public domain
 
+// REQUIRES the following Arduino libraries:
+// - DHT Sensor Library: https://github.com/adafruit/DHT-sensor-library
+// - Adafruit Unified Sensor Lib: https://github.com/adafruit/Adafruit_Sensor
+
 #include "DHT.h"
 
-#define DHTPIN 2     // what digital pin we're connected to
+#define DHTPIN 2     // Digital pin connected to the DHT sensor
+// Feather HUZZAH ESP8266 note: use pins 3, 4, 5, 12, 13 or 14 --
+// Pin 15 can work but DHT must be disconnected during program upload.
 
 // Uncomment whatever type you're using!
 //#define DHTTYPE DHT11   // DHT 11
@@ -25,7 +31,7 @@ DHT dht(DHTPIN, DHTTYPE);
 
 void setup() {
   Serial.begin(9600);
-  Serial.println("DHTxx test!");
+  Serial.println(F("DHTxx test!"));
 
   dht.begin();
 }
@@ -44,7 +50,7 @@ void loop() {
 
   // Check if any reads failed and exit early (to try again).
   if (isnan(h) || isnan(t) || isnan(f)) {
-    Serial.println("Failed to read from DHT sensor!");
+    Serial.println(F("Failed to read from DHT sensor!"));
     return;
   }
 
@@ -53,17 +59,15 @@ void loop() {
   // Compute heat index in Celsius (isFahreheit = false)
   float hic = dht.computeHeatIndex(t, h, false);
 
-  Serial.print("Humidity: ");
+  Serial.print(F("Humidity: "));
   Serial.print(h);
-  Serial.print(" %\t");
-  Serial.print("Temperature: ");
+  Serial.print(F("%  Temperature: "));
   Serial.print(t);
-  Serial.print(" *C ");
+  Serial.print(F("°C "));
   Serial.print(f);
-  Serial.print(" *F\t");
-  Serial.print("Heat index: ");
+  Serial.print(F("°F  Heat index: "));
   Serial.print(hic);
-  Serial.print(" *C ");
+  Serial.print(F("°C "));
   Serial.print(hif);
-  Serial.println(" *F");
+  Serial.println(F("°F"));
 }

keywords.txt

@@ -12,11 +12,11 @@ DHT	KEYWORD1
 # Methods and Functions (KEYWORD2)
 ###########################################
 
-begin KEYWORD2
-readTemperature KEYWORD2
-convertCtoF KEYWORD2
-convertFtoC KEYWORD2
-computeHeatIndex KEYWORD2
-readHumidity KEYWORD2
-read KEYWORD2
+begin	KEYWORD2
+readTemperature	KEYWORD2
+convertCtoF	KEYWORD2
+convertFtoC	KEYWORD2
+computeHeatIndex	KEYWORD2
+readHumidity	KEYWORD2
+read	KEYWORD2
 

library.properties

@@ -1,5 +1,5 @@
 name=DHT sensor library
-version=1.3.0
+version=1.3.4
 author=Adafruit
 maintainer=Adafruit <info@adafruit.com>
 sentence=Arduino library for DHT11, DHT22, etc Temp & Humidity Sensors